Question

Basicity means replaceable H⁺ ions but what is meant by replaceable H⁺ ions ?

Answer 1

I hope you have an idea of ionic and covalent bonds. Covalent bonds are of 2 types, polar and non polar.

Ionic bond is between a positive and negative ions, H+ and a negative ion. When a polar solvent like water is added, these bonds are easily broken.

Polar covalent bond is when H is bonded with highly electronegative atoms like oxygen, sulfur,etc.
Again, when polar solvent like water is added, these bonds are broken.

we say polar solvent because water has 2H attatched to O, and bond between them is polar covalent.

Non polar bond is when H is bonded with atoms like Carbon. These bonds, being non polar, cannot be broken by addition of polar solvent like water.

All hydrogen in an atom bonded by polar bond or a by ionic bond, as stated earlier, these bonds can be easily broken, by solvent like water, and hence such H is called replacable H atoms.

H atoms attatched by non polar bonds, cannot be seperated by solvent, so are non replacable.

in
CH3COOH, one H in COOH is attached to Oxygen, O. So, bond is polar, and H is replacable.

while 3H in CH3 are attatched to Carbon. As bond is non polar, we call those 3 H as non replacable.

In HCl, bond is ionic, so replacable again.